Evaluating the Short-Term Associations between PM2. 5, Black Carbon, and Cardiovascular Diseases in a Large Developing Megacity

BACKGROUND: An association between ambient air pollution and cardiovascular disease (CVD) have been demonstrated by many epidemiological studies in developed countries, however few studies have been performed in developing countries of Asia. OBJECTIVE: In this study, we evaluated fine particulate matter and black carbon (BC), and their impacts on CVD health in Karachi, Pakistan.
METHODS: Yearlong (2008-2009) PM2.5 samples were collected at 2 sites at 24-hour intervals; a commercial-residential and industrial-residential site. Daily records of hospitalizations and ER visits for CVDs were collected at the 3 major tertiary hospitals serving Karachi. BC measurements were obtained from PM2.5 filters using an optical transmissometer. Generalized linear time-series models were utilized to analyze daily counts of hospital, meteorological, and pollutant data over 0 to 3 day lags.
RESULTS/DISCUSSION: PM2.5 concentrations ranged from 27 to 279 µg/m3. Daily mean BC concentrations varied from 1 to 32µg/m3. Higher effect estimates per 1 µg/m3 for BC compared with PM2.5 were observed. Effect estimates were generally higher with BC from Tibet Center, the commercial-residential site, compared with Korangi, the industrial-residential site. These results suggest BC concentrations were associated with CVD health effects that were not reflected quantitatively when modeled with PM2.5.
CONCLUSION: This study provides new scientific evidence of the magnitude of CVD health effects associated with air pollution in an urban center of a large developing nation, and provides Pakistani officials with important information for policy planning. BC is a valuable additional air quality indicator for evaluating health risks from combustion-derived particles in developing megacities.